94 THE EXTERNAL ANATOMY 



small triangular portion between the elytra at their bases. The 

 elytra are hard and sufficiently large to completely cover the 

 entire upper surface of the abdomen ; they are somewhat irregu- 

 larly and indistinctly striated longitudinally, there being seven 

 striae between the suture and the humeral prominence. It may be 

 noted, that this projection at the shoulders is a very common 

 feature in all those beetles that have large membranous wings ; 

 it appears to be a necessary consequence of the room taken up 

 under the elytra, by the wings near their attachment to the 

 metathorax when folded.* 



The metathorax — which is so far united to the mesothorax, 

 that the line of separation can scarcely be distinguished — carries 

 on its under side, or metasternum, the posterior pair of legs, and 

 on its upper side, or metanotum, the pair of membranous wings. 

 These are the organs of flight, and when extended are large and 

 ample, and as they are obviously too large to lie under the elytra 

 extended, they are constructed for folding, which is attained by 

 the great costal nervure having a hinge-like joint about one-third 

 of its length from the tip, so that the tip portion shuts up until it 

 takes up a position at about right angles to the rest of the costa, 

 and the membranous portion naturally falls into folds ; in this way 

 they lie compactly under the elytra concealed and protected. 



The only portion now remaining to be described is the 

 abdomen, consisting of nine rings, which fit one into the other 

 like a telescope ; they are soft on the upper side, where they are 

 protected by the wings and elytra, but are chitinous on the under 

 side. The terminal rings, however, on the upper side, are harder 

 than the rest, being more or less exposed, particularly the last one, 

 which in some beetles is very important, and is called the 

 pygidium. The rings are best seen on the upper side, as, owing to 

 the great space taken up by the meso- and meta- sternum for the 

 attachment of the coxae, the first rings are much contracted on the 

 under side. They are joined together by an elastic membrane, 

 particularly at the lateral margins, on the upper side, where there 

 is a soft portion, in which are situated the abdominal spiracles. 



* Another species, G. nmtator (Marsham), has nine stria between the 

 suture and this prominence. 



